You could create a Master Page/Topic Template and define a Header or Footer that contains the code. Then you could select all the topics and associate the Master Page/Topic Template with all the topics to rapidly propagate the code.
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Thanks for sharing this solution - I also took that way for a cookie management tool embedding but during output generation, that script is put into the <head> twice.
Does anyone know how to avoid that?
RoboHelp 2020 on Windows, Frameless output (HTML5).